As a preliminary to or during a surgical intervention it is often necessary to adapt and match implants and other surgical elements to anatomical circumstances. The anatomical circumstances can be determined for example by the curvature of a bone or the course of a fracture. In order to adapt surgical elements to anatomical circumstances, the surgeon has a wide range of instruments at his disposal. This range of instruments includes for example cutting forceps, bending forceps, plate benders and similar instruments.
From U.S. Pat. No. 4,474,046 three-point bending forceps for surgical rods are known. The bending forceps have two branches that can swivel about a common axis of rotation. A bending punch is provided in the region of the common axis of rotation. Two counter bearings are associated with the bending punch, which are formed on free ends of the branches. When the branches are actuated the bending punch remains fixed and the two counter bearings execute movements on elliptical paths about the bending punch. As a result of these movements a rod arranged between the bending punch and the counter bearings is bent around the bending punch. In order to be able to bend rods of different diameter (or achieve different bending radii), the bending punch has an outer contour that differs from section to section. By rotating the bending punch about the axis of rotation of the branches a desired contour section can be chosen, by means of which the bending punch is to co-operate with the rod to be bent.
U.S. Pat. No. 5,490,409 discloses further three-point bending forceps with a rotatable, eccentrically mounted bending punch. In order to be able to stop the rotatable bending punch with certainty at a desired angular setting, a mechanism is provided with two arms coupled to one another via a joint. A guide pin is arranged in the region of the joint, which pin executes a linear movement when the bending forceps are actuated. At the same time the guide pin slides within a channel formed on the rear side of the bending punch in order to lock the bending punch at a fixed angle.
From U.S. Pat. No. 5,651,283 multifunctional bending forceps for linear bone plates are known. By means of the bending forceps a linear bone plate can be bent in a preferred plane of the bone plate and can also be bent outwardly from the preferred plane. The bending of the bone plate in the preferred plane is effected by means of a three-point mechanism. The three-point mechanism comprises two counter bearings provided in the head region of a first branch, as well as a bending punch that is formed on a mouth section swivellably mounted in the head region of the first branch. The mouth section is coupled via a linkage to a second branch. A connecting arm between the first and the second branch is guided via its first end within a slit formed in the first branch and is linked via its second end to the second branch.
It has been found that the approach known from U.S. Pat. No. 5,651,283, namely to provide the bending punch on a swivellable mouth section, has disadvantages. One disadvantage is for example the fact that the bending punch can be deflected only to a limited extent. On account of this limited deflectability the area of application of the bending forceps is basically limited to bone plates with narrowly defined geometrical dimensions.
From DE 103 01 692 A1 further three-point bending forceps are known. The bending forceps comprise a bending punch which can swivel relative to two counter bearings. In contrast to the bending forceps of U.S. Pat. No. 5,651,283, a sufficient deflectability of the bending punch is ensured, so that bone plates of different geometrical dimensions can be bent. However, during a bending procedure the swivelling movement of the bending punch can have a destabilising effect on the position of the bone plate to be bent.
The object of the present invention is to provide bending forceps for surgical elements such as bone plates, which have a wide area of application and provide a precise bending. A further object of the present invention is to provide a bending forceps system comprising the bending forceps.